Hensley Arrow: How does it REALLY work?
There have been several discussions on this hitch that have become somewhat 'controversial'. I am NOT trying to stir this controversy/bashing back up. Instead, I'd like to see a good, intelligent di...
Forum Discussion
The pendulum analogy doesn't work very well because of the effect of gravity, especially as it pertains to a TT. I'd like to modify that analogy to make it more applicable.
Imagine that both the TV and TT have hockey pucks at the bottom of each tire (or a single large puck halfway between the centers of the two axles of each vehicle) and they are sitting on water-slickened ice. You would then see that you can't "turn" (pivot) either vehicle without the other one being forced to pivot as well. The difference is that the vehicle on the end of the hitch that has the long-long link does not pivot as far as the one on the short-long link when a bend at the hitch occurs. That's one of the reasons the TV is placed at that end of the HA. If the hitch were somehow reversed, a small turn of the TV would require a larger twist of the TT. This makes it impractical to arrange the hitch this way because it gives the TT greater "leverage" over the TV.
It's important to characterize something like this in order to understand the tendancies all the tires are being faced with. If you'll remember my "entertaining" model, you may or may not have noted that I had to twist each end bar in just a certain way in order to get it to "play" at all. Virtually any other direction of force results in no movement at all. Like it or not, playing with the model really does help one more fully appreciate the great advantage the TV has with a HA compared to a conventional hitch setup. I would suggest that we throw out the moment illustrations I presented because I'm not sure they properly characterize the complex translations that are required in order for a pivot to occur. Since the HA has no simple pivot point like a conventional hitch possesses, I think it would be extremely difficult to ever make a fair mathematical comparison between the two hitches.
Tim
Imagine that both the TV and TT have hockey pucks at the bottom of each tire (or a single large puck halfway between the centers of the two axles of each vehicle) and they are sitting on water-slickened ice. You would then see that you can't "turn" (pivot) either vehicle without the other one being forced to pivot as well. The difference is that the vehicle on the end of the hitch that has the long-long link does not pivot as far as the one on the short-long link when a bend at the hitch occurs. That's one of the reasons the TV is placed at that end of the HA. If the hitch were somehow reversed, a small turn of the TV would require a larger twist of the TT. This makes it impractical to arrange the hitch this way because it gives the TT greater "leverage" over the TV.
It's important to characterize something like this in order to understand the tendancies all the tires are being faced with. If you'll remember my "entertaining" model, you may or may not have noted that I had to twist each end bar in just a certain way in order to get it to "play" at all. Virtually any other direction of force results in no movement at all. Like it or not, playing with the model really does help one more fully appreciate the great advantage the TV has with a HA compared to a conventional hitch setup. I would suggest that we throw out the moment illustrations I presented because I'm not sure they properly characterize the complex translations that are required in order for a pivot to occur. Since the HA has no simple pivot point like a conventional hitch possesses, I think it would be extremely difficult to ever make a fair mathematical comparison between the two hitches.
Tim
